*{
    margin: 0;
    padding: 0;
  
  }
  body{
    /*设置窗口的高度为100%的窗口高度*/
    height: 100vh;
    /*伸缩盒子模型*/
    display: flex;
    /*下面两个属性让body里的子类居中*/
    justify-content: center;
    align-items: center;
    background-color: #2c3e50 ;
  }
  .container{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    width: 300px;
    height: 450px;
    border-radius: 20px;
    background-color:#34495e;
    box-shadow: 15px 15px 10px rgba(33,45,0,3);
    overflow: hidden;
    position: relative;
  }
  .container form{
    width: 300px;
    height: 200px;
    display: flex;
    justify-content: space-around;
    flex-direction: column;
    align-items: center;
    z-index: 1;
  }
  .container form .tbx{
    width: 200px;
    height: 40px;
    outline: none;
    border-bottom: 1px solid #ffffff;
    background:none;
    color: #fff;
  }
  /*设置placeholder */
  .container form .tbx::placeholder{
    color: #ffffff;
    font-size: 15px;
  }
  .container form .sub{
    width: 200px;
    height: 40px;
    outline: none;
    border: 1px solid #ffffff;
    border-radius: 20px;
    letter-spacing: 5px;
    color:#ffffff;
    background: none;
    cursor: pointer;
  }
  .contain h1{
    z-index: 1;
    color: #ecf0f1;
    letter-spacing: 5px;
    padding-left: 5px;
    font-size: 50px;
    font-weight: 100;
    text-shadow: 5px 5px 5px rgba(33,45,58,0.3);
  }
  /*设置鼠标进入的样式*/
  .container .in{
    position: absolute;
    top: 0;
    left: 0;
    display: block;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: #3498bd;
   transform: translate(-50%,-50%);
    /*使用in动画，持续0.5s，缓出的时间函数，停留在最后一帧*/
    animation: in 0.5s ease-out forwards;
  }
  /*设置鼠标离开的样式*/
  .container .out {
    position: absolute;
    top: 0;
    left: 0;
    display: block;
    width: 1200px;
    height: 1200px;
    border-radius: 50%;
    background: #3498bd;
    transform: translate(-50%, -50%);
    /*使用in动画，持续0.5s，缓出的时间函数，停留在最后一帧*/
    animation: out 0.5s ease-out forwards;
  }
  /*设置鼠标进入时，元素的动画*/
  @keyframes  in{
    /*初始关键帧*/
    0%{
      width: 0;
      height: 0;
    }
    /*结尾关键帧*/
    100%{
      width: 1200px;
      height: 1200px;
    }
  }
  /*设置鼠标离开使，元素的动画*/
  @keyframes  out{
    /*初始关键帧*/
    0%{
      width: 1200px;
      height: 1200px;
    }
    /*结尾关键帧*/
    100%{
      width: 0;
      height: 0;
    }
  }